Datasheet

7
LTC2902
2902f
UU
U
PI FU CTIO S
COMP3 (Pin 1): Comparator Output 3. Nondelayed, active
high logic output with weak pull-up to V2. Pulls high when
V3 is above reset threshold. May be pulled greater than V2
using external pull-up.
COMP1 (Pin 2): Comparator Output 1. Nondelayed, active
high logic output with weak pull-up to V2. Pulls high when
V1 is above reset threshold. May be pulled greater than V2
using external pull-up.
V3 (Pin 3): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V
or ADJ. See Table 1 for details.
V1 (Pin 4): Voltage Input 1. Select from 5V or 3.3V. See
Table 1 for details. The greater of (V1, V2) is also V
CC
for
the chip. Bypass this pin to ground with a 0.1µF (or
greater) capacitor.
CRT (Pin 5): Reset Delay Time Programming Pin. Attach
an external capacitor (C
RT
) to GND to set a reset delay time
of 4.6ms/nF. Leaving the pin open generates a minimum
delay of approximately 50µs. A 47nF capacitor will gener-
ate a 216ms reset delay time.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
RST Pull-Up Current vs V2
(LTC2902-1)
RST Pull-Up Current vs V2
(LTC2902-2)
INPUT OVERDRIVE ABOVE THRESHOLD (mV)
COMPX PROPAGATION DELAY (µs)
250
200
V1, V2
V3, V4
150
2902 G22
0
100
50
1000
10 100
T
A
= 25°C
V2 (V)
2
0
PULL-UP CURRENT (µA)
4
8
12
2.5
3
3.5 4
2902 G23
4.5
16
20
2
6
10
14
18
5
T
A
= 25°C
V
RT25
V
RT30
V
RT33
V2 (V)
2
0
PULL-UP CURRENT (mA)
2
4
5
2.5
3
3.5 4
2902 G24
4.5
1
3
6
5
T
A
= 25°C
V
RT25
V
RT30
V
RT33
COMPX Propagation Delay vs
Input Overdrive Above Threshold
COMPX Pull-Up Current
vs V2 (COMPX Held at 0V)
V2 (V)
1
0
PULL-UP CURRENT (µA)
2
6
8
10
20
14
2
3
3.5
2902 G21
4
16
18
12
1.5 2.5
4
4.5
5
T
A
= 25°C